While the mine workings are small the overlying rocks support themselves of and the full pressure does not come upon the mine Caving p i llars.
The caving-in of the mine, however, is rarely so complete that avenues of escape are not open.
He knew it, which meant he was counting on her caving at some point.
Although petroleum wells in Russia have not the depth of many of those in the United States, the disturbed character of the strata, with consequent liability to caving, and the occurrence of hard concretions, render drilling a lengthy and expensive Drilling in operation.
In the working of thick deposits the block of ground between two levels is divided into horizontal sections or floors which are worked either from above downward or from of Thick the bottom upward; in the first case the separate floors are worked by one of the caving systems; in the second, generally with the aid of filling.